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We demonstrate, both theoretically and experimentally, that a sandwich-type structure consisting of a thin LiNbO 3 slab and Si prism outcoupler can be an efficient convertor of unamplified laser pulses into broadband terahertz radiation. Pumping a 1 cm long sandwich structure with a 35 μm thick LiNbO 3 slab by 8 nJ, 100 fs optical pulses from Ti: sapphire oscillator we achieved the conversion efficiency of 0.8× 10− 4⁠, ie, two orders of magnitude higher than in the conventional generation scheme with ZnTe crystal. Using laser oscillator as a pump has an advantage of high repetition rate and, therefore, potentially high signal-to-noise ratio (∼ 50 dB in our experiment).